MODAPS PCR 06-008
| PCR Number | 06-008 |
|---|---|
| Date | 2006-07-14 |
| Initiator | Richard Frey |
| Abstract | Improved method for selecting final Cloud Top Pressure algorithm using Clear Sky Bias data. |
| Problem Statement | The MOD06CT algorithm (CO2-slicing) uses calculated clear-sky radiances in the computation of cloud top pressures (CTPs). There are systematic errors inthese calculations that may be mitigated by application of bias correctionfactors in the MODIS bands used (33-36). Also, in some middle and highlatitude scenes, spuriously high clouds were reported. These are reduced innumber by use of a new method of choosing a final CTP solution from among theseveral available. |
| Description of Change | MOD06CT will read in 1-degree zonal clear-sky bias (mean observed minus calculated) values computed over 8 days for each of bands 33-36. These biases will be added to the clear-sky calculation used in each cloud top pressure retrieval. In addition, a constant representing measurement biases in each of bands 34-36 will be added. These were estimated from radiance comparisons with Scanning HIS. A "top-down" method of choosing a final CTP solution is also implemented. |
| Products Affected | MOD06_L2 |
| Software Affected | PGE06 |
| Processing String to Receive the Change | Terra Forward, Terra Reprocessing |
| Downstream Product Effects | All products using cloud top pressure, cloud top temperature, or effective cloud amount as input. |
| Data Granules to be Used for Science Testing | Several global days. |
| Justification | See justification for Aqua processing, as the same logic applies to Terra. The "top-down" method for choosing final CTPs reduces the number of spuriously high clouds reported (CTPs too low). |
| Effective Date for Implementation of Change | Start of C5 Terra Reprocessing. |
| Status | PI approved. Michael King approved for Atmosphere, Vincent Salomonsom approved. |
